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We present a novel spectral Mueller matrix measurement system for both elastic and inelastic scattering (fluorescence)
polarimetric measurements. The system comprises of a Xenon lamp as excitation source, a polarization state generator
(PSG) and a polarization state analyzer (PSA) unit to generate and analyze polarization states required for 4 x 4 sample
Mueller matrix measurements, coupled to a spectrometer for spectrally resolved (λ ~ 400 - 800 nm) signal detection.
The PSG unit comprises of a fixed linear polarizer (polarization axis oriented at horizontal position) followed by a
rotatable broadband quarter wave plate. The sample-scattered light is collected and collimated using an assembly of
lenses, then passes through the PSA unit, and is finally recorded using the spectrometer. The PSA unit essentially
consists of a similar arrangement as that of the PSG, but positioned in reverse order, and with the axis of the linear
polarizer oriented at vertical position. A sequence of sixteen measurements are performed by changing the orientation of
the fast axis of the quarter wave plates of the PSG unit (for generating the four required elliptical polarization states) and
that of the PSA unit (for analyzing the corresponding polarization states). The orientation angles
(35°, 70°, 105° and 140°) were chosen based on optimization of the PSG and PSA matrices to yield most stable system
Mueller matrices. The performance of the polarimeter was calibrated using Eigenvalue calibration method which also
yielded the actual values of the system PSG and PSA matrices at each wavelength. The system has been automated and
is capable of Mueller matrix measurement with high accuracy over the entire spectral range 400 - 800 nm (elemental
error < 0.01). For recording the elastic scattering Mueller matrix of sample, the PSG and PSA matrices for each
wavelength are used, while for fluorescence Mueller matrix measurements, the PSG for the excitation wavelength
(chosen to be 405 nm) and PSA for varying emission wavelengths (450 - 800 nm) are used. The developed spectral
Mueller matrix system has been initially used to record both elastic scattering and fluorescence Mueller matrices from
normal and cancerous cervical tissues.
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